Speedboats have a major shortcoming. Although they may be fast and powerful, speedboats are extremely inefficient. Even in gliding mode, many speedboats maintain considerable contact with water. The resistance of water (as compared to the resistance of air) requires tremendous expenditures of fuel from ships moving at high speeds. As vessels “plow the water,” or as gliding vessels strike the surface of the water, much energy is lost to friction. For example, fuel consumption by a ship exceeds several-fold the consumption by a truck of similar size, traveling on wheels over the surface.
Speedboats present may safety hazards. A boat moving at high speeds, in direct contact with the surface of the water faces the risk of puncturing the hull by colliding with debris or hitting a reef, just under the surface of the water. In choppy seas, speedboats may capsize or sustain structural damage from stress caused by collision with the waves at high speeds and wrong angles. The resistance of water can at any time turn the kinetic energy of a fast-moving vessel against that vessel, as it collides and “burrows” into a wave. In order to prevent such occurrences, speedboats must limit their speed in anything but the calmest waters. As planing is impossible at low speeds, the fuel consumption is further increased.
Vessels on hydrofoils also present many shortcomings. Stability at high speed is compromised. Maneuverability at high speeds is limited. The wing-like foils are vulnerable to collisions and damage with floating debris. Functionality of the foils is reduced in the presence of waves, as foils, with small area of support underneath, sink into the waves.
Many vessels on hydrofoils rely on the use of special turbines for channeling air under the hull to raise the vessel onto the foils. Such turbines are an additional and significant source of power consumption. Furthermore, the foils are usually installed at an angle to the horizontal surface. The angle allows for the lift, required to raise much of the hull over the surface of the water. At the same time, the lift is produced by resistance of the foil against the water. The necessary resistance unavoidably reduces efficiency and increases fuel consumption of the vessel.
Although ships on hydrofoils can be fast, they do not approach the speeds of aircraft. Vessels of such design are also a great cause of injury to whales, dolphines and other marine animals.
One solution over the limitations of the high-speed watercraft is to raise the craft above the surface of the water. Such solution has been attempted on the wing-in-ground vehicles, otherwise referred to as “ekranoplans,” the most famous of which were developed for the Soviet navy by Rostislav Alexeev's constructor's bureau.
The term “ground effect” refers to the reduction in drag experienced by an aircraft as it approaches a height approximate to the size of the wingspan's length off the ground, sea, or other level surface. The effect increases as the wing descends closer to the ground, with the most significant effects occurring at a height of one half the wingspan length above the ground. The ground effect can otherwise be described as the cushion of high-pressure air created by the aerodynamic interaction between the wings and the surface.
Alexeev's designs showed very encouraging characteristics and tremendous promise. The “ekranoplans,” of which the “Caspian Sea Monster” was the most famous, were some of the largest aircraft ever built, with a length of 73 m, rivaling that of the Hughes H-4 Hercules “Spruce Goose” and many modern jumbo jets. Their cargo load was far beyond the load imaginable with an airplane, and the speeds far exceeded anything possible with sea surface vessels. Tests of the Lun-class rocket-carrier ekranoplan also showed much improved stealth, speed, and operating costs, as compared to conventional rocket-carrying naval vessels.
Ekranoplans have been the subject of great interest for navies around the world, including the US navy. Several ekranoplans even entered service with the Soviet navy in the 1980s-1990s, although deficiencies in design prevented and still prevent the widespread use of ground-effect craft. One important deficiency was the lack of stability in flight. Another deficiency was the fact that this new unique vehicle type was designed, using the preconceptions of existing airplanes. Soviet Ekranoplans, as well as modern ground effect vehicles use traditional aircraft designs and solutions, to build what is essentially a marine vessel.
In fact, Soviet ekranoplans look exactly like large airplanes, except for the slightly-clipped wingspan. Such vehicles/vessels have little stability when idly floating on water or at low speeds. Large wing area makes them extremely prone to tipping over from gusts of wind or waves. This makes them dangerous to use, and all but unusable for one of their main intended purposes—as marine rescue vehicles.
Traditional airplane design, with wide wings and narrow fueselage, evolved for best performance at high speed in thin air, a medium with resistance 650 times less than that of water. The design of Alexeev's ekranoplans and their progeny is ill adopted for use on water or in direct proximity to water. The fragility was illustrated all too clearly when “Caspian Sea Monster” fell apart in test “flight” upon striking a wave.
In light of the shortcomings associated with traditional high-speed vessels and ground-effect craft, there is a long-standing and unsatisfied need in the art for a fast and economical craft. The craft should have the speed characteristics comparable with those of the ekranoplans, yet have seaworthy hull that will be stable at low and high speeds. The craft should be strong and capable of withstanding the impact of the waves. The craft should have aphibious capabilities, allowing the operation of craft at high speeds over water, as well as over ice, snow and other surfaces. The craft should also have the ability to rise above the height of the ground effect to pass over difficult terrain or stormy sea surface. The amphibious craft of the present invention achieves these objectives and provides numerous other benefits.